The following relates to document processing systems. It finds particular application in conjunction with background detection and suppression and will be described with a particular reference thereto. However, it is to be appreciated that the following is also amenable to other like applications.
Typically, in a digital reproduction device, a document or image is scanned by a digital scanner which converts the light reflected from the document into electrical charges representing the light intensity from predetermined areas (pixels) of the document. The pixels of image data are processed by an image processing system which converts the pixels of image data into signals which can be utilized by the digital reproduction machine to recreate the scanned image.
Sometimes the white regions of the original image are not imaged as white regions in the produced document. Typically, digital scanning and multifunction devices provide the function of automatic background suppression to make white regions in the original white on scanned images or copies. Background detection is important for correct application of suppression techniques. For example, the mistakes in dynamic range detection could result in defects ranging from loss of highlight or shadow details to residual dots in white background.
One particular problem arises in pasted documents. For example, each of the documents, which are pasted together, could have a different background as an original. The likelihood of making mistakes in dynamic range detection in pasted documents is increased. Another particular problem arises in wide format scanners and documents. The size of some documents, such as 36″ wide x 100′ long, might make the background in the rendered image substantially non-uniform throughout the rendered document. In most cases, there is not enough contrast between the background and the foreground text.
One approach to detect the background pixels is to use the traditional lead edge based background detection methods as, for example, described in U.S. Pat. No. 6,198,845 to Tse, identified below. However, such methods may produce numerous mistakes. Another approach to detecting background value of a document is to use full page background detection approaches as described in U.S. Pat. No. 6,674,899 to Nagarajan, identified below. But, the full page background detection of the wide format documents is problematic with such methods due to the size of the documents and hence high costs.
The alternative approach is a manual background detection in which a user or an operator checks the background and selects an appropriate suppression mechanism. However, such technique is time consuming, user “unfriendly”, and is unreliable as it depends on user's perception of the image.
There is a need for methods and apparatuses that overcome the aforementioned problems and others.